Many types of wells, e.g. oil and gas wells, are completed in multiple stages. A lower stage of the completion is moved downhole on a running string and may comprise either a stand-alone screen or a screen with a gravel pack in the annulus between the screen and the open hole or casing. After the lower completion running string is retrieved, an upper stage of the completion is deployed.
In many applications, it is desirable to instrument the lower completion with electrical or optical sensors or to provide for transmission of fluids to devices in the lower completion. For example, a fiber optic cable can be placed in the annulus between the screen and the open or cased hole. To enable communication of signals between the sensor in the lower completion and the surface or seabed, a wet-mate connection is needed between the upper and lower completion equipment.
Optical, electrical and fluid wet-mate connectors typically are designed as discrete stand-alone components. The stand-alone connectors are mated in a downhole environment that can be full of debris and contaminants. For instance, the mating can take place after an open hole gravel pack which creates a high probability for substantial amounts of debris and contaminants in the wellbore at the vicinity of the connectors during the mating sequence. Existing discrete optical, electrical and fluid wet-mate connectors have proven to be very susceptible to contamination by debris during the mating process.
Furthermore, the discrete nature of the connectors results in an unfavorable geometry that can be difficult to integrate into the completion equipment. The outer diameter of the completion equipment must fit within the inner casing diameter. A centralized, large diameter inner port also is needed to provide access for service equipment into the lower completion and to provide a large flow area for production or injection of fluids. The remaining annular space is not well suited to the typical circular cross section of discrete connectors. This limitation compromises the overall design of the completion equipment and also limits the total number of channels that can be accommodated within a given envelope.
The geometry of the discrete connectors also increases the difficulty of adequate flushing and debris removal from within and around the connectors prior to and during the mating sequence. Attempts to protect the connectors from debris and/or to provide adequate flushing have lead to completion equipment designs that have great complexity with an undesirable number of failure modes.